NDLI: Defective dicubanes of $Co^{II}/Co^{III}$ complexes with triethanolamine and N-donors

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Dendrinou-samara, C. Psycharis, V. Hosseinian, S. R. Tangoulis, V. Menelaou, M. Raptopoulou, C. P.
Description	Author Affiliation: Hosseinian SR ( Department of General and Inorganic Chemistry, School of Chemistry, Aristotle University of Thessaloniki, Thessaloniki, 54124, Greece.)
Abstract	The mixed valence $Co^{II}/Co^{III}$ tetranuclear clusters $[Co^{II}_{2}Co^{III}_{2}(tea)_{2}(pyr)_{2}(NO_{3})_{4}]·2CH_{3}CN$ (1), $[Co^{II}_{2}Co^{III}_{2}(μ_{3}-OH)_{2}(Htea)_{2}(bpy)_{4}](NO_{3})_{4}$ (2), and $[Co^{II}_{2}Co^{III}_{2}(μ_{3}-OH)_{2}(Htea)_{2}(phen)_{4}](NO_{3})_{4}·2CH_{3}CN·2CH_{3}OH$ (3) are described where tea and Htea are the fully and the doubly deprotonated form of triethanolamine, while as N-donors are pyridine, 2,2′-bipyridine and 1,10-phenanthroline. Complexes 1–3 contain the $Co^{II}_{2}Co^{III}_{2}O_{6}$ core and can be described as defective dicubanes with different imperfectness. In 1, the central rhombic core $Co_{2}O_{2}$ is occupied by two $Co^{III}$ ions while the external cobalt atoms display $Co^{II}$ oxidation states; meanwhile 2 and 3 exhibit a reversal in their $Co^{II}_{2}Co^{III}_{2}$ oxidation state distribution. Two different theoretical models were used to explain the magnetic behavior: (i) spin–spin interaction model with local anisotropy terms where S = 3/2 for both metal centers and (ii) an anisotropic spin–spin interaction model applicable in the low temperature range (T < 40 K) using effective spins $(S_{eff}$ = 1/2) for both metal centers. For 1 a relatively strong next-nearest-neighbour antiferromagnetic exchange interaction between the Co(II) centers which are connected via diamagnetic Co(III) ion was found while for 2 and 3 the presence of ferromagnetic interaction is confirmed. The fitting results, concerning the first model, gave: J = 2.0(2)/3.2(2)/3.8(2) $cm^{−1},$ g = 2.35(1)/2.52(1)/2.57(1) and D = 11.0(1)/8.5(1)/7.8(1) $cm^{−1}$ while concerning the second model are: $J_{z}$ = −7.1(2)/19.2(2)/22.1(2) $cm^{−1},$ $g_{z}$ = 6.8(1)/8.1(1)/8.3(1), $J_{xy}/J_{z}$ = 0.34(2)/0.11(2)/0.14(2), and $g_{xy}/g_{z}$ = 0.52(2)/0.28(2)/0.36(2) for 1–3. X-Band EPR spectrum of 1 has a very broad derivative centered at g = 5.3 while for 2 and 3 large g-variations were found in the range 20.0–1.0, indicative of an exchange interaction between Co(II) ions.
ISSN	14779226
Issue Number	15
Volume Number	42
e-ISSN	13645447
Journal	Dalton Trans.
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2013-04-21
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Cobalt Chemistry Coordination Complexes Ethanolamines 2,2'-Dipyridyl Chemical Synthesis Crystallography, X-Ray Magnetics Molecular Conformation Oxidation-Reduction Phenanthrolines Temperature Journal Article
Content Type	Text
Resource Type	Article
Subject	Inorganic Chemistry

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